Image processing circuit and method for image processing

Abstract

A circuit and a method for image processing are provided. The image processing circuit has an adaptor and a sharpening circuit. The adaptor has a processing unit and a weight generator. The processing unit receives an input video signal, and the input video signal has information of a plurality of pixels. The processing unit processes the input video signal to calculate a color difference value of a target pixel of the pixels. The weight generator generates a weighting signal according to the color difference value. The sharpening circuit performs a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal.

1. An image processing circuit, comprising:
 an adaptor, comprising:
 a processing unit, for receiving an input video signal comprising information of a plurality of pixels, and for processing the input video signal to determine a color difference value corresponding to a target pixel according to chromatic information of at least two pixels adjacent to the target pixel; and 
 a weight generator, coupled to the processing unit, for generating a weighting signal according to the color difference value, wherein the weighting signal comprises a weighting value of the target pixel; and 
 
 a sharpening circuit, coupled to the adaptor, for performing a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal, wherein the sharpening circuit comprises:
 a first multiplier, coupled to the adaptor, for multiplying the weighting value of the target pixel by a gain such that the sharpening circuit performs the sharpening operation on the input video signal according to the weighting signal and the gain to generate the sharpened video signal. 
 
 
     
     
       2. The image processing circuit of  claim 1 , wherein the chromatic information of each of the at least two adjacent pixels comprises a first chrominance Cb and a second chrominance Cr. 
     
     
       3. The image processing circuit of  claim 2 , wherein the processing unit calculates the color difference value of the target pixel according to a first chrominance and a second chrominance of a first pixel and a first chrominance and a second chrominance of a second pixel, the first and the second pixels being adjacent to the target pixel. 
     
     
       4. The image processing circuit of  claim 3 , wherein the color difference value equals (|Cb(1)−Cb(2)|+|Cr(1)−Cr(2)|)/2, Cb(1) and Cr(1) are the first chrominance and the second chrominance of the first pixel respectively, and Cb(2) and Cr(2) are the first chrominance and the second chrominance of the second pixel respectively. 
     
     
       5. The image processing circuit of  claim 3 , wherein the first chrominance Cb and the second chrominance Cr serve as two reference axes of a chromatic coordinate system, the chromatic coordinate system comprises four regions {(Cb, Cr)|Cb≦Cb 2 , Cr≦Cr 2 }, {(Cb, Cr)|Cb≧Cb 1 , Cr≦Cr 2 }, {(Cb, Cr)|Cb≦Cb 2 , Cr≧Cr 1 }, and {(Cb, Cr)|Cb≧Cb 1 , Cr≧Cr 1 }, where Cb 2 >Cb 1 >0, Cr 2 >Cr 1 >0, the first and the second chrominances of the first pixel are Cb(1) and Cr(1), the first and the second chrominances of the second pixel are Cb(2) and Cr(2), and the possessing unit determines the color difference value according to region(s) of the chromatic coordinate system where coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) are located. 
     
     
       6. The image processing circuit of  claim 5 , wherein when the coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) lie in a same region of the four regions, the color difference value equals 0. 
     
     
       7. The image processing circuit of  claim 5 , wherein when the coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) lie in two different regions of the four regions, the color difference value equals √{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}. 
     
     
       8. The image processing circuit of  claim 5 , wherein when the coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) lie in two different regions of the four regions, the color difference value equals (|Cb(1)−Cb(2)|+|Cr(1)−Cr(2)|). 
     
     
       9. The image processing circuit of  claim 3 , wherein the target pixel is located at the middle point of the first and the second pixels. 
     
     
       10. The image processing circuit of  claim 1 , wherein the weighting value is a monotonic decreasing function of the color difference value. 
     
     
       11. The image processing circuit of  claim 10 , wherein the weight generator interpolates the weighting value of the target pixel according to at least two predetermined color difference values and corresponding weighting values. 
     
     
       12. The image processing circuit of  claim 1 , wherein the weight generator looks up the weighting value of the target pixel from a lookup table according to the color difference value. 
     
     
       13. An image processing circuit, comprising:
 an adaptor, comprising:
 a processing unit, for receiving an input video signal comprising information of a plurality of pixels, and for processing the input video signal to determine a color difference value corresponding to a target pixel according to chromatic information of at least two pixels adjacent to the target pixel; and 
 a weight generator, coupled to the processing unit, for generating a weighting signal according to the color difference value, wherein the weighting signal comprises a weighting value of the target pixel; and 
 
 a sharpening circuit, coupled to the adaptor, for performing a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal, wherein the sharpening circuit comprises:
 a high-pass filter, for receiving the input video signal and high-pass filtering the input video signal to generate a high frequency video signal; 
 a coring circuit, coupled to the high-pass filter, for eliminating a core portion of the high frequency video signal to generate a coring video signal; 
 a second multiplier, coupled to the weight generator and the coring circuit, for multiplying the coring video signal by the weighting signal to generate a sharpened signal; 
 a delay unit, for receiving and delaying the input video signal to generate a delayed video signal; and 
 an adder, coupled to the second multiplier and the delay unit, for adding up the sharpened signal and the delayed video signal to generate the sharpened video signal. 
 
 
     
     
       14. The image processing circuit of  claim 13 , wherein the chromatic information of each of the at least two adjacent pixels comprises a first chrominance Cb and a second chrominance Cr. 
     
     
       15. The image processing circuit of  claim 14 , wherein the processing unit calculates the color difference value of the target pixel according to a first chrominance and a second chrominance of a first pixel and a first chrominance and a second chrominance of a second pixel, the first and the second pixels being adjacent to the target pixel. 
     
     
       16. The image processing circuit of  claim 13 , wherein the weighting value is a monotonic decreasing function of the color difference value. 
     
     
       17. An image processing circuit, comprising:
 an adaptor, comprising:
 a processing unit, for receiving an input video signal comprising information of a plurality of pixels, and for processing the input video signal to determine a color difference value corresponding to a target pixel according to chromatic information of at least two pixels adjacent to the target pixel; and 
 a weight generator, coupled to the processing unit, for generating a weighting signal according to the color difference value, wherein the weighting signal comprises a weighting value of the target pixel; and 
 
 a sharpening circuit, coupled to the adaptor, for performing a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal, wherein the sharpening circuit comprises:
 a low-pass filter, for receiving and low-pass filtering the input video signal to generate a low frequency video signal; 
 a coring circuit, coupled to the low-pass filter, for eliminating a core portion of the low frequency video signal to generate a coring video signal; 
 a second multiplier, coupled to the weight generator and the coring circuit, for multiplying the coring video signal by the weighting signal to generate a sharpened signal; 
 a delay unit, for receiving and delaying the input video signal to generate a delayed video signal; and 
 a subtractor, coupled to the second multiplier and the delay unit, for subtracting the sharpened signal from the delayed video signal to generate the sharpened video signal. 
 
 
     
     
       18. The image processing circuit of  claim 17 , wherein the chromatic information of each of the at least two adjacent pixels comprises a first chrominance Cb and a second chrominance Cr. 
     
     
       19. The image processing circuit of  claim 18 , wherein the processing unit calculates the color difference value of the target pixel according to a first chrominance and a second chrominance of a first pixel and a first chrominance and a second chrominance of a second pixel, the first and the second pixels being adjacent to the target pixel. 
     
     
       20. The image processing circuit of  claim 17 , wherein the weighting value is a monotonic decreasing function of the color difference value. 
     
     
       21. An image processing method, comprising:
 receiving and processing an input video signal comprising information of a plurality of pixels; 
 determining a color difference value corresponding to a target pixel according to the input video signal, wherein the color difference value is determined according to chromatic information of at least two pixels adjacent to the target pixel; 
 generating a weighting signal according to the color difference value, wherein the weighting signal comprises a weighting value of the target pixel; and 
 performing a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal, wherein the step of performing the sharpening operation comprises:
 multiplying the weighting value of the target pixel by a gain; and 
 performing the sharpening operation on the input video signal according to the weighting signal and the gain to generate the sharpened video signal. 
 
 
     
     
       22. The image processing method of  claim 21 , wherein the chromatic information comprises a first chrominance Cb and a second chrominance Cr. 
     
     
       23. The image processing method of  claim 22 , wherein the step of determining the color difference value corresponding to the target pixel comprises:
 calculating the color difference value of the target pixel according to a first chrominance and a second chrominance of a first pixel and a first chrominance and a second chrominance of a second pixel, the first and the second pixels being adjacent to the target pixel. 
 
     
     
       24. The image processing method of  claim 23 , wherein the color difference value equals (|Cb(1)−Cb(2)|+|Cr(1)−Cr(2)|)/2, Cb(1) and Cr(1) are the first chrominance and the second chrominance of the first pixel respectively, and Cb(2) and Cr(2) are the first chrominance and the second chrominance of the second pixel respectively. 
     
     
       25. The image processing method of  claim 23 , wherein the first chrominance Cb and the second chrominance Cr serve as two reference axes of a chromatic coordinate system, the chromatic coordinate system comprises four regions {(Cb, Cr)|Cb≦Cb 2 , Cr≦Cr 2 }, {(Cb, Cr)|Cb≧Cb 1 , Cr≦Cr 2 }, {(Cb, Cr)|≦Cb 2 , Cr≧Cr 1 }, and {(Cb, Cr)|Cb≧Cb 1 , Cr≧Cr 1 }, where Cb 2 >Cb 1 >0, Cr 2 >Cr 1 >0, the first and the second chrominances of the first pixel are Cb(1) and Cr(1), the first and the second chrominances of the second pixel are Cb(2) and Cr(2), and the color difference value is determined according to the region(s) where coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) are located. 
     
     
       26. The image processing method of  claim 25 , wherein when the coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) are located in a same region of the four regions, the color difference value equals 0. 
     
     
       27. The image processing method of  claim 25 , wherein when the coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) are located in two different regions of the four regions, the color difference value equals √{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}{square root over ((Cb(1)−Cb(2)) 2 +(Cr(1)−Cr(2)) 2 )}. 
     
     
       28. The image processing method of  claim 25 , wherein when the coordinates (Cb(1),Cr(1)) and (Cb(2),Cr(2)) are located in two different regions of the four regions, the color difference value equals (|Cb(1)−Cb(2)|+|Cr(1)−Cr(2)|). 
     
     
       29. The image processing method of  claim 23 , wherein the target pixel is located at the middle point of the first and the second pixels. 
     
     
       30. The image processing method of  claim 21 , wherein the weighting value is a monotonic decreasing function of the color difference value. 
     
     
       31. The image processing method of  claim 30 , wherein the step of generating the weighting signal comprises:
 interpolating the weighting value of the target pixel according to at least two predetermined color difference values and corresponding weighting values. 
 
     
     
       32. The image processing method of  claim 21 , wherein the step of generating the weighting signal comprises:
 looking up the weighting value of the target pixel from a lookup table according to the color difference value. 
 
     
     
       33. An image processing method, comprising:
 receiving and processing an input video signal comprising information of a plurality of pixels; 
 determining a color difference value corresponding to a target pixel according to the input video signal, wherein the color difference value is determined according to chromatic information of at least two pixels adjacent to the target pixel; 
 generating a weighting signal according to the color difference value, wherein the weighting signal comprises a weighting value of the target pixel; and 
 performing a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal, wherein the step of performing the sharpening operation comprises:
 high-pass filtering the input video signal to generate a high frequency video signal; 
 eliminating a core portion of the high frequency video signal to generate a coring video signal; 
 multiplying the coring video signal by the weighting signal to generate a sharpened signal; 
 delaying the input video signal to generate a delayed video signal; and 
 adding up the sharpened signal and the delayed video signal to generate the sharpened video signal. 
 
 
     
     
       34. The image processing method of  claim 33 , wherein the chromatic information comprises a first chrominance Cb and a second chrominance Cr. 
     
     
       35. The image processing method of  claim 34 , wherein the step of determining the color difference value corresponding to the target pixel comprises:
 calculating the color difference value of the target pixel according to a first chrominance and a second chrominance of a first pixel and a first chrominance and a second chrominance of a second pixel, the first and the second pixels being adjacent to the target pixel. 
 
     
     
       36. The image processing method of  claim 33 , wherein the weighting value is a monotonic decreasing function of the color difference value. 
     
     
       37. An image processing method, comprising:
 receiving and processing an input video signal comprising information of a plurality of pixels; 
 determining a color difference value corresponding to a target pixel according to the input video signal, wherein the color difference value is determined according to chromatic information of at least two pixels adjacent to the target pixel; 
 generating a weighting signal according to the color difference value, wherein the weighting signal comprises a weighting value of the target pixel; and 
 performing a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal, wherein the step of performing the sharpening operation comprises:
 low-pass filtering the input video signal to generate a low frequency video signal; 
 eliminating a core portion of the low frequency video signal to generate a coring video signal; 
 multiplying the coring video signal by the weighting signal to generate a sharpened signal; 
 delaying the input video signal to generate a delayed video signal; and 
 subtracting the sharpened signal from the delayed video signal to generate the sharpened video signal. 
 
 
     
     
       38. The image processing method of  claim 37 , wherein the chromatic information comprises a first chrominance Cb and a second chrominance Cr. 
     
     
       39. The image processing method of  claim 38 , wherein the step of determining the color difference value corresponding to the target pixel comprises:
 calculating the color difference value of the target pixel according to a first chrominance and a second chrominance of a first pixel and a first chrominance and a second chrominance of a second pixel, the first and the second pixels being adjacent to the target pixel. 
 
     
     
       40. The image processing method of  claim 37 , wherein the weighting value is a monotonic decreasing function of the color difference value.